Fujimori remains under investigation over undeclared financial contributions to her 2011 presidential campaign.

An appeals judge has freed Peruvian opposition leader Keiko Fujimori, a week after she was arrested in an ongoing corruption investigation.

The daughter of Peru's former strongman leader, Alberto Fujimori, cried as the judge read his ruling on Wednesday night and was heckled by critics as she left the court.

Fujimori remains under investigation over undeclared financial contributions to her 2011 presidential campaign, totalling some $1.2m. At least 19 others have been arrested in the case.

The money is alleged to have come from Brazilian construction giant Odebrecht, part of one of Latin America's largest-ever corruption scandals, affecting politicians and business leaders in more than 10 countries.

A twice-defeated presidential candidate, Fujimori has led the powerful conservative opposition party, Popular Force, which has a majority in Congress, since her father's arrest in 2007.

She was a key figure in toppling former President Pedro Pablo Kuczynski in March over his own ties to Odebrecht.

Since June, prosecutors have been investigating allegations that three former presidents took bribes disguised as campaign funds from Odebrecht, which is at the centre of political scandals across Latin America.

Former presidents Kuczynski, Alan Garcia and Alejandro Toledo all took undeclared campaign contributions in exchange for promises to offer lucrative contracts to Odebrecht, prosecutors said.

Fujimori's arrest came a week after her 80-year-old father's presidential pardon for crimes against humanity was revoked by a top court.

Following his extradition from Japan to Peru in 2007, Alberto Fujimori was sentenced to 25 years in prison for commanding death squads that massacred civilians in a counterinsurgency campaign during his right-wing government. He was later found guilty of corruption.

Keiko Fujimori's legal troubles could help President Martin Vizcarra, who threatened to dissolve Congress last month to pressure the opposition to pass his proposed judicial and political reforms.

Fujimori has always denied the charges against her, saying that she is a victim of political persecution.

In a handwritten statement on Twitter on the day of her arrest, Fujimori said she had been persecuted for 18 years without proof against her ever being presented.